Quality and Reliability Methods - SAS

Chapter 7 Multivariate Control Charts 111
Control Chart Usage
4. Select the Steam Turbine Targets.jmp table that was saved in phase 1 and click Open.
5. Click OK on the launch window that appears.
By default, the T Square Chart, at the top of the report, shows a UCL, which is calculated with an alpha
level of 0.05. Change this alpha level by clicking on the red-triangle icon of the Multivariate Control Chart
platform and selecting Set Alpha Level. Several alpha level options are provided, including 0.01, 0.05,
0.10, 0.50, and Other (for example, to set the alpha level to 0.001).
1. Select Other.
2. Type 0.001 into the dialog window asking you to specify the alpha level for the upper control limit.
3. Click OK.
A new T Square Chart is displayed with an UCL calculated using your specified alpha (0.001 in this
example). Figure 7.5 shows the T Square Chart with the UCL based on an alpha level of 0.001.
Figure 7.5 Phase 2 Steam Turbine Control Chart
As shown in Figure 7.5, out-of-control conditions occur at observations 2, 3, 4, 5, and 8. This result implies
that these observations do not conform to the historical data of Steam Turbine Historical.jmp, and that the
process should be further investigated.
Monitoring a Grouped Process
The workflow for monitoring a multivariate process with grouped data is similar to the one for ungrouped
data. An initial control chart is used to create target statistics, and these statistics are used in monitoring the
process.
For example, open Aluminum Pins Historical.jmp, which monitors a process of manufacturing aluminum
pins. Enter all the Diameter and Length variables as Y, Columns and subgroup as the Subgroup. After
clicking OK, you see the chart shown in Figure 7.6.